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Cálculo



Concepts to cover:

There are two things to consider when learning calculus:
  1. Differentiation
  2. Integration

Let's talk about something that we all like-- Fast Cars.
We want a car to travel from point A to point B. We want to travel at a high speed to minimize the time required for the trip. Also, we enjoy the high speed, and also the acceleration we use to achieve high speed.
Our car that travels at a constant velocity makes the calculus more simple. We can use the function d=200h where d is distance in kilometers and t is time in hours. If we travel two hours, we travel 400 kilometers [400=200(2)].
Now we are ready to discuss the meaning of the words integrate and differentiate. We differentiate the function that gives distance to determine the function that gives velocidad. We differentiate the function that gives velocity to determine the function that gives acceleration.


Integration works in the opposite direction. We integrate the function that gives acceleration to calculate the function that gives velocity. We integrate the function that gives velocity to calculate the function that gives distance.
The derivative of a function that is a constant is zero. If we travel in our fast car at a constant speed, there is no acceleration. If the odometer, which is equivalent to distance, is not changing, then our velocity is zero.
If we set acceleration to a constant, then velocity will be an increasing function. Distance (relative to our starting point) will increase.
The force of gravity on earth is equivalent to an acceleration rate of 9.8 meters per second. If we accelerate a space ship at 9.8 meters per second we will simulate Earth gravity, which is good for the well being of the crew. We can calculate the velocity as a function of time using v=9.8t, where v is velocity in meters per second, and t is time in seconds. It should make sense that after the first second our velocity will be 9.8 meters per second, and after the second second, 19.6 meters per second.
Now we introduce some notation. The derivative of f (x) is f ' (x). The derivative of f ' (x) is f " (x). We'll leave it at that for now.
If f (x)=xn then f ' (x)=nxn-1.
If f(x)=x2 then f ' (x)=2x.
If f(x)=2x then f'(x)=2x0, and since x0=1, we write f'(x)=2, and we say that the function f'(x) is a constant.
Now we are ready to integrate. If we integrate the constant 2, the result is the function 2x + C, where C is a constant. If we integrate the function 2x + C, the result is the function x2 + Cx + D, where D is also a constant.
Every time that we integrate, we must add on an unknown constant to the function. If we are integrating speed to determine the reading on the odometer, the constant would be reading of the odometer at time=0. If my friend drives a car out of the factory, and I follow behind him in my car, we will both travel using the same velocity function, but our odometer readings will differ by a contant.
A definite integral is an indefinte integral that has been given two boundaries. You can integrate a work function to get the function that tells how much energy was required to do the work. If you want to know how much energy was required from time T=0 to time T=3 (maybe your units are hours), then you integrate from T=0 to T=3, and you get a number for your answer. Thus, an indefinite integral of a function is another function, but the definite integral of a function is a number.
Now, to explain how calculus relates to a graph. The line on the graph plots the information contained in a function. The derivative of the function gives the slope of the function. For the blue line, the function rises six squares as it runs six squares, and since 6/6=1, we say the slope is 1. For the green line, which is steeper, the function rises six squares as it runs three, and since 6/3=2, we say the slope is 2.
Integration of the function tells the area under the curve. If the constant of integration is zero, then the result provides the area down to the y=0 line. The area under the blue line is 18 squares (.5 + 1.5 + 2.5 + 3.5 + 4.5 + 5.5 = 18). The function for the blue line is f(x)=x. You may remember writing y=x, which means the same thing. When we integrate f(x)=x, the result is the function 0.5x2. The function starts at the point (0,0) and ends at (6,0). Therefore, we integrate over the range from 0 to 6. (

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